Herb & supplement monograph

Niacinamide Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Niacinamide interacts with medications. The heart of this page is the interaction list — every drug Niacinamide is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Niacinamide is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Niacinamide Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Niacinamide drug interaction appears low for most people. None of the listed interactions are rated major, and while over a hundred medications are rated moderate, the supporting evidence is limited to case reports or theory rather than well-controlled human studies.

Interactions deserving the most attention

The strongest signal involves warfarin, where one report described a person whose blood-thinning level rose sharply after adding niacinamide, raising a possible bleeding concern. Case reports in children also suggest niacinamide may slow the body's clearance of the seizure medications carbamazepine and primidone, which could raise their levels and side effects. People on hemodialysis who take blood thinners or antiplatelet drugs may deserve extra care, since low platelet counts have been reported in that group, though this effect is not well established.

What the rest of the list means

A long list of moderate interactions does not mean every combination is harmful. Most of these are theoretical, based on how niacinamide might affect enzymes the body uses to clear certain medications, and their real-world importance has not been confirmed in people.

Check your medications against Niacinamide

Based on HelloPharmacist’s Niacinamide interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Niacinamide

124 medications have a known interaction with Niacinamide, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Niacinamide using our pharmacist-reviewed interaction data.

AI summaries are generated from our Niacinamide interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Niacinamide combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Niacinamide affects

Every type of medication (drug category) Niacinamide is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 4 drug categories Niacinamide interacts with

Anticoagulant/antiplatelet DrugsCarbamazepine (tegretol)Primidone (mysoline)Warfarin (coumadin)

Anticoagulant/Antiplatelet Drugs

Theoretically, niacinamide may have additive effects when used with anticoagulant or antiplatelet drugs, especially in patients on hemodialysis.
Several cases of thrombocytopenia have been reported for hemodialysis patients treated with niacinamide 1 gram daily. Hemodialysis patients receiving niacinamide had almost a three-fold higher risk of developing thrombocytopenia when compared with those receiving placebo.

Likelihood Unlikely Evidence D

Carbamazepine (Tegretol)

Niacinamide might increase the levels and adverse effects of carbamazepine.
Plasma levels of carbamazepine were increased in two children given high-dose niacinamide, 60-80 mg/kg/day. This might be due to inhibition of the cytochrome P450 enzymes involved in carbamazepine metabolism. There is not enough data to determine the clinical significance of this interaction.

Likelihood Possible Evidence D

Primidone (Mysoline)

Niacinamide might increase the levels and adverse effects of primidone.
Case reports in children suggest niacinamide 60-100 mg/kg/day reduces hepatic metabolism of primidone to phenobarbital, and reduces the overall clearance rate of primidone; however, there is not enough data to determine the clinical significance of this potential interaction.

Likelihood Possible Evidence D

Warfarin (Coumadin)

There is limited evidence that niacinamide may increase the anticoagulant effects of warfarin.
In a case report, a patient on warfarin developed an elevated international normalized ratio (INR) of 8.4 after taking niacinamide 500 mg twice daily for 10 days. The patient's INR was previously stable, ranging between 2 and 3, with no other changes to current medications or diet reported. The elevated INR returned to the therapeutic range after receiving vitamin K and discontinuing niacinamide.

Likelihood Possible Evidence D

Monograph

Niacinamide: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Niacinamide (also called nicotinamide) is a form of vitamin B3 used in supplements and skin-care products. It is well established for preventing and treating vitamin B3 deficiency, and there is moderate evidence for some skin uses, but many popular claims are still being studied. It is generally well tolerated at usual doses, but high amounts should be discussed with your doctor or pharmacist.

Part used: Not applicable (a form of vitamin B3)
Common forms: Tablets, capsules, powders, topical creams and serums

People commonly use it for

Acne and skin health
Pellagra (niacin deficiency)
Anti-aging and skin tone
Rosacea
Protecting against certain skin cancers

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Usually well tolerated at recommended amounts, but high doses can cause side effects and should be supervised.

PregnancyLikely Safe

When used orally in amounts that do not exceed the tolerable upper intake level (UL) for niacinamide. The UL of niacinamide during pregnancy and lacta...

Read the full pregnancy detail

BreastfeedingLikely Safe

When used orally in amounts that do not exceed the tolerable upper intake level (UL) for niacinamide. The UL of niacinamide during pregnancy and lacta...

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Niacinamide, also known as nicotinamide, is one of the active forms of vitamin B3. It is not a plant or herb. Instead, it is a water-soluble vitamin that the body can make from the amino acid tryptophan and that is found in foods like meat, fish, eggs, dairy, and fortified grains.

In supplements, niacinamide is used to prevent or treat vitamin B3 deficiency. It is also a very popular ingredient in skin-care products such as serums, creams, and acne treatments. Niacinamide is closely related to niacin (nicotinic acid), but it does not usually cause the warm, tingling "flushing" feeling that niacin can.

How it works

Niacinamide is a building block for two important molecules in the body called NAD and NADP. These help cells turn food into energy, repair DNA, and carry out many normal chemical reactions.

On the skin, niacinamide is thought to help strengthen the skin barrier, reduce water loss, calm inflammation, and affect how the skin makes oil and pigment. Many of these effects come from laboratory studies and smaller clinical trials, so the exact way it helps any one condition is not always fully understood.

Effectiveness

Does Niacinamide work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 32 uses evaluated

1 Likely effective 4 Possibly effective 1 Leans ineffective 26 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

Likely Effective Pellagra